54061-38-0Relevant articles and documents
Hydrogen isotope fractionation factors for N,N-dimethylbenzyl-ammonium ion and some related species: An unusually strong preference for deuterium over protium
Guo, Hong-Xun,Kresge, A. Jerry
, p. 295 - 298 (2007/10/03)
Deuterium fractionation factors were determined by the 1H and 13C NMR methods in aqueous solution for PhCH2NLMe2+ (φ = 1.47 ± 0.05), PhCH2OL (φ = 1.04 ± 0.06), PhCO2L (φ = 1.04 ± 0.08), and CH3CO2L (φ = 0.99 ± 0.02). The medium effect for transferring PhCH2NMe2 from H2O to D2O, Φ = 1.025 ± 0.003, was also determined by partitioning this substance between water and immiscible organic solvents, and a UV spectroscopic method was used to measure the solvent isotope effect on the acid ionization of PhCH2NLMe2+, (Qa)H/(Qa)D = 4.88 ± 0.16. This solvent isotope effect agrees well with the value predicted using the relevant fractionation factors, (Qa)H/(Qa)D = 4.38 ± 0.28. The unusually large value of φ for PhCH2NLMe2+ is attributed to stiffened bending vibrations of its N-L bond imposed by the tetrahedral structure of the ion and the bulk of its methyl groups.
A systematic entropy relationship for the general-base catalysis of the deprotonation of a carbon acid. A quantitative probe of transition-state solvation
Bunting, John W.,Stefanidis, Dimitrios
, p. 779 - 786 (2007/10/02)
The general-base-catalyzed deprotonation of a carbon acid, the l-methyl-4-(phenylacetyl)pyridinium cation (pKa = 9.02 at 25 °C), has been investigated for 32 general-base catalysts (25 amines and seven phenoxide ions) in aqueous solution. Amines give a generally scattered Bronsted plot; ring-substituted benzylamines have ?= 0.52, and ring-substituted phenoxides have ?= 0.60, with the phenoxides being more reactive than amines of similar basicity. The temperature dependences of the general-base-catalyzed deprotonation of this carbon acid have been measured over the range 15-45 °C for 12 base catalysts (eight primary, secondary, and tertiary amines; 4-(dimethylamino)pyridine; two phenoxide ions; hydroxide ion). The entropies of activation for these deprotonations show a clean curvilinear dependence upon the entropies of protonation of these base species, with the hydroxide ion being the only significant deviant from this relationship. This observation quantitatively establishes the importance of solvation effects as the major source of deviations that are commonly observed in Bronsted relationships for general-base-catalyzed processes.